There continues to be growing recognition that exercise and inactivity can play important roles in many disease processes. The goal of this training grant proposal is to establish a strong and rich research training environment for those M.D.s and Ph.D.s interested in exercise science. The underlying programmatic theme of this training program is that of "integrative/translational" science. Within this context, the prgoram consists of two core groups: the Molecular Physiology Core Group and the Systems Physiology Core Group. The emphasis of these cores is in skeletal muscle, cardiovascular, and respiratory physiology given that these areas of research represent the focus of the Program Faculty, and represent areas of extensive on-going interactions. An integrated/translational approach is especially important in exercise science because of the profound role that physical activity is now known to play in human health. Postdoctoral fellows will interact with the faculty and other trainees through a formal didactic program, seminars, journal clubs, and research-in-progress discussions. At the beginning of the program each fellow will work with the Executive Committee to select a primary and secondary research emphasis designed to reflect an appropriate diversity of topics in exercise science. These emphases will be selected from the two cores. Trainees will become familiar with a variety of animal and cell model systems and state-of-the-art approaches to human performance testing, thereby facilitating the translation from these systems to human research and, ultimately to clinical applications. For this latter objective, Human Performance Laboratory at the U.C. Irvine GCRC/CTSC will play an important role as it is funded specifically to support translational research in an environment that optimizes the safety and quality of human investigation. The Program Faculty have a history of collaborative research with each other and are currently involved in training postdoctoral research fellows. This proposed training program is designed to introduce postdoctoral trainees to new disciplines as they continue to hone skills and approaches mastered in the predoctoral years. For postdoctoral MD.s, the program will attract individuals seriously interested in becoming independent investigators. Exercise physiology is not a separate ACGME-recognized specialty or subspecialty;consequently, MDs pursuing postdoctoral training in this program must be committed to academic careers. For Ph.D.s, the program will be best suited for basic scientists who see their academic careers involving clinical interaction either through direct human research or as members of faculties of medical schools where translational research activity is likely to be encouraged.